Many types of equipment, particularly those associated with the electronic art, often require a relatively small flow of cooling water to prevent over-heating of delicate and costly components. For example, the large vacuum tubes used by high-power radio transmitters require cooling, which is usually by a flow of water through cooling coils surrounding the tube envelope. If the flow of water accidentally stops, there would be serious over-heating problems and possible damage to the equipment. Similarly, a flow of cooling water is often necessary to cool components being subjected to electron bombardment or sputtering in vacuum deposition equipment to prevent melting or other costly damage to the various components and materials.
There are many types of flow indicators available, most of which indicate the quantity of flow through the system. The present invention comprises a small transparent fluid flow indicator particularly suitable for mounting behind a circular hole in an instrument panel, such as is used to mount controls, gauges and meters associated with the vacuum deposition system. The indicator includes a small paddle wheel which is very readily visible through the transparent cover of the indicator and the rotation which will indicate the approximate fluid flow to the equipment operator. The paddle wheel has six blades, each containing a small bar magnet so that rotation of the paddle wheel will generate an alternating magnetic field that is sensed by a pickup coil in the indicator housing adjacent to the paddle wheel. The output of the coil may then be amplified and applied to a relay circuit that will be actuated by the fluid flow and generation of the magnetic field and which may be used to sound an alarm if the fluid is prevented from flowing through the indicator.